on 4 September 2011. The booster fired for 140 seconds and again had nominal performance through the test. A third test, ST-03, was conducted on 14 June 2015 to validate the changes from the sub-orbital test flight data. Human rated variant of S200 or HS200 was developed for the Gaganyaan programme. The first static fire test of HS200 was conducted on 13 May 2022 at SDSC SHAR for a duration of 135 seconds with no issues. L110 static fire tests ISRO conducted the first static test of the L110 core stage at its Liquid Propulsion Systems Centre (LPSC) test facility at Mahendragiri, Tamil Nadu on 5 March 2010. The test was planned to last 200 seconds, but was terminated at 150 seconds after a leakage in a control system was detected. A second static fire test for the full duration was conducted on 8 September 2010. C25 stage tests The first static fire test of the C25 cryogenic stage was conducted on 25 January 2017 at the ISRO Propulsion Complex (IPRC) facility at Mahendragiri, Tamil Nadu. The stage fired for a duration of 50 seconds and performed nominally. A second static fire test for the full in-flight duration of 640 seconds was completed on 17 February 2017. This test demonstrated consistency in engine performance along with its sub-systems, including the thrust chamber, gas generator, turbopumps and control components for the full duration. Modifications after LVM3-X After the suborbital test flight of GSLV Mk III, certain modifications were made to the vehicle to improve its performance. The propellant grain geometry of the head end segments were changed from a 10-lobed slotted configuration to a 13-lobed star configuration and propellant load was reduced to to improve performance during transonic phase of flight. The payload fairing was modified to an ogive shape, and the S200 booster nosecones and inter-tank structure were redesigned to have better aerodynamic performance. Vehicle design The first stage consists of two S200 solid motors, also known as Large Solid Boosters (LSB) attached to the core stage. Each booster is wide, long, and carries of hydroxyl-terminated polybutadiene (HTPB) based propellant in three segments with casings made out of M250 maraging steel. It is the largest solid-fuel booster after the Space Shuttle SRBs and Ariane 5 SRBs. The flex nozzles can be vectored up to ±8° using electro-hydraulic actuators operating in blow-down mode and are used for vehicle control during the